Commutator



Dec. 26, 1950 ac; WAHLBERG COIIIUTATOR Filed 001;. 4, 1948 IN V EN TOR.

ER! C C. WAHLBERG ATTORNEY.

aliases Dec. 26, 1950 COMMUTATOR Eric C. Wahlberg, Stamford, Conn.,assignor to Electrolux Corporation, Old Greenwich, Conn... a corporationof Delaware Application October 4, 1948, Serial No. 52,727

9 Claims. 1

My invention relates to commutators for electric motors, and moreparticularly to commutators of the type wherein a metal blaik, whichultimately is to form the bars, is stamp-d from a flat sheet withanchoring tabs extending from opposite edges of the blank, the blankthereafter being wrapped around a hub structure, the tabs bent inwardlyto anchoring position and the blank thereafter slotted to form theindividual bars.

Heretofore, in the manufacture of commutators of this type, it has beencustomary to use a rigid insulating material, such as a phenolic resincondensation product, for the hub structure in order to insulate thebars from each other. However, while material of this nature may besuitable for motors which operate without substantial increase incommutator temperature, it has proved to be unsuitable for powerful highspeed motors, due chiefly to the fact that ozone, which is produced as aresult of commutator sparking, reacts chemically with the material atthe high temperatures prevailing, which reaction reduces the originallyrigid material to a granular state with an attendant loss of mechanicalstrength.

One of the objects of my invention is to provide a commutator of thistype, which however is not subject to the above disadvantage, whilestill being relatively inexpensive. This I accomplish by providing a hubof metal which has ample mechanical strength and is not adverselyaffected by heat and ozone. This hub is insulated from the commutatorbars by being encased in two cup-shaped members of insulating material,preferably made of moulded paper impregnated with an insulatingcompound. These cups are economical to manufacture and to apply to themetal hub.

In order to simplify the slotting operation after the blank has beensecured to the hub struc ture, 1' form portions of the slots by theinitial stamping operation. This not only reduces the length of cutnecessary to complete the separation of the bars, but also assures thatall of the metal which has to be cut is directly and firmly supported bythe hub structure, which assures that it is cleanly and completely outthrough and that no burs or bridges are left between the bars.

A further object of my invention is the provision of improved means forsecuring the armature leads to the commutator bars. To this end, atongue is struck up from each of the anchor tabs on one side of theblank, this preferably being done as a part of the initial stampingoperation. These tongues are so positioned with respect to the tabs thatwhen the latter are bent inwardly to anchoring position, the tongues areautomatically caused to extend outwardly at a suitable angle to the axisof commutator so that the leads may be wrapped around them. Thiseliminates the usual staking operation heretofore employed to secure theleads in short slots formed in the bars.

Further objects and advantages of my invention will be apparent from thefollowing description considered in connection wit the accompanyingdrawings, which form a part of this specification and of which:

Fig. 1 is a cross-sectional view, taken on the line il of Fig. 2, of aportion of an armature of an electrical motor embodying a commutator inaccordance with my invention;

Fig. 2 is an end view of the commutator shown in Fig. 1;

Fig. 3 is a perspective view on an enlarged scale of a metal blank whichis employed in the construction of the commutator shown in the precedingfigures; and

Fig. 4 is a perspective view of member.

Referring more particularly to Fig. 3, reference character It!designates generally a metal blank stamped from sheet copper or anyother metal suitable for use as the bars of a commutator. This blankincludes a continuous central portion II from the opposite side edges ofwhich extend aligned projections it. The root portions of theseprojections H, which are adjacent to the continuous central portion 82,have straight sides, as is indicated at It, whereas the tip portionshave tapered sides as shown at 18. A tongue 20 is struck out of each ofbhe projections It on one side of the central portion. The materialforming the tongue is severed from the projection along two sides andone end of the tongue, the opposite end of the tongue remaining integralwith the projection This juncture between the tongue and the projectionis substantially in alignment with the juncture between the straight andtapered portions of the projection.

Figs. 1 and 2 show a completed commutator in assembled relation on thearmature shaft 22 of an electrical motor. The commutator includes a hubmember 24 made preferably of steel or other suitable material which hasa high mechanical strength and is not adversely affected by hightemperatures and ozone. Hub 24 is formed with an insulating an annularflange 26 at each end thereof. The

hub is encased within two cup-shaped members 28 made of insulatingmaterial. As is shown more particularly in Fig. 4, each of the membersIt includes a skirt portion ill, the inner diameter of which issubstantially equal to the outer diameter of the hub 24, and an endportion 32 which has a configuration conforming to the end of the hub24. The end portion 32 is formed with a central opening 34 through whichextends the armature shaft 22. Preferably, the members 23 are made ofmoulded paper impregnated with a suitable insulating compound.

As above stated, two of the cup-shaped members 2e are employed to encasethe metal hub 26, one being slipped on to the hub from each end andconsequently the ends of the skirt portions 30 are in abuttingrelationship. The skirt portions serve to insulate the cylindrical outersurface of the metal hub 24, while the end por= tions 32 provideinsulation at the ends of the hub. If desired, a strip 35 of mica orother suitable insulating material may be wrapped around the skirtportions so as to bridge the joint between their abutting ends, while atthe same time increasing the thickness of the insulation around thecylindrical portion of the hub.

The blank it is thereafter wrapped around the insulated hub 26 and theprojections it are bent inwardly so as to engage around the flanges 26,thus securely anchoring the blank, the eup= shaped members 28 and thestrip 36 to the hub. The parts are so dimensioned that the axial lengthof the hub 26, including the flanges 25 is substantially equal to thedistance a as shown on Fig. 3. Consequently, before the projectionsare-bent into clamping position, only the tapered end portions thereofextend axially beyond the hub and hence the bending begins at about thejuncture of the straight and tapered portions. The end portions are madetapered so that, when bent inwardly around the flanges of the hub, thereis sufiicient'clearance between adjacent projections so that they do notoverlap or contact each other.

The bending of the projections in this manner automatically causes thetongues 20 to extend outwardly at a substantial angle with respect tothe unbent portion of the blank, as is shown clearly in Fig. 1. Thisresults from the fact that each tongue is joined to the projection inthe region where the latter is bent and is separated from the unbentportion.

After blank III has been secured to the hub structure in a manner abovedescribed, it is slotted to form separate commutator bars by cuttingthrough the central portion l2 between the inner ends of the straight sded slots. By forming these straight sided slots during the initialstamping operation the length. of the cutting required to completelyseparate the bars is obviously reduced, thus speeding up this operation,and in addition all of the metal which has to be removed during thecutting operation is directly and firmly supported by the hub structure.circular saw which, because of the soft nature of copper, would be aptto draw out the metal any place where it were not firmly supported,instead of cutting all the way through. If this were to occur therewould remain an electrical connection between adjacent bars.

The purpose of the tongue 20 is to provide means for securing thearmature leads 40 to the commutator bars. Heretofore, it has been thepractice to bring out excessively long leads during the winding of thearmature, which leads are subsequently secured to the bars, as by stak-This cutting operation is performed by 'a j ing them into small slotsformed in the bars and thereafter cutting on the excess length. With thetongues at. on the other hand, it is unnecessary to bring outexcessively long leads, inasmuch as the leads may be looped around thetongue which, as is shown in Fig. I. extend at an angle and away fromthe armature winding. This not only saves a certain amount of material,but completely eliminates the separate staking operation. in order toobtain a good electrical connection between the leads and the tongues,solder may be applied where the loam are looped around the tongues. orthe tongues may be bent down slightly after the leads have been loopedtherearound in order to clamp the leads between the tongues and theadjacent portions of the bars. Moreover, should a tongue ac cidentallybe completely sheared from the bar. the lead may be staked in theconventional manner into the slot thus formed.

As is customary, a piece of tape 62 may be wound around the leads 46 inorder to hold them securely in place to thus prevent them from howingoutwardly under the action of centrifugal force.

If desired, washers 3d may be placed at each end of the hub and withinthe inturned ends of the projections it. i have found it suitable to usefelt washers which, when saturated with impregnating compound during theregular impregnating of the completed armature, become rigid and serveto prevent the inturned ends of the projections from moving inwardlyaway from the flanges 25. Hence, the washers aid in looking theprojections in anchoring position.

Instead of completing the slotting of the commutator immediately afterthe blank has been secured to the ,hub and before the latter is mountedon the armature shaft, this step may be performed after the armature hasbeen wound and impregnated. This has the advantage that the impregnatingcompound cannot get in the central portions of the slots and thecompound which does get in the preformed end portions,

- is removed during the cutting step, thus eliminating the necessity ofa separate operation for removing the compound from the slots.Furthermore, the preformed end portions of the slots are ordinarilyoutside of the brush track, and hence it is immaterial if compoundremains in these portions.

While I have shown and described one more or less specific embodiment ofmy invention it is to be understood that this has been done forillustrations only and the scope of my invention is not to be limitedthereby but is to be determined by the appended claims.

What I claim is:

1. In a commutator, a cylindrical metal hub, a pair of insulatingmembers each having a cylindrical skirt portion and an end wall formedmembers insulating said tabs from the end sur-.

faces of the hub.

2. In a commutator. a cylindrical metal hub having an axially extendingperipheral flange an end wall conforming to the flanged end of said hub,said insulating members enclosing said hub to insulate the cylindricaland end surfaces thereof, a plurality of commutator barscircumferentially disposed around the insulated hub, and an anchor tabextending from each end of each bar, said tabs being bent inwardlyaround said flanges to secure said bars, said insulating members andsaid hub in assembled relationship.

3. In a commutator, a cylindrical metal hub, a pair of insulatingmembers each having a cylindrical skirt portion and an end wall formedwith a central aperture, said insulating members enclosing said hub withthe ends of the skirt portions adjacent to each other to insulate thecylindrical and end surfaces of the hub, a band of insulating materialsurrounding both skirt portions and bridging the joint between theadjacent ends thereof to increase the thickness of the insulation on thecylindrical surface of the hub, a plurality of commutator barscircumferentially disposed around the insulated hub, and anchor tabsextending radially inwardly from said bars for securing the latter, saidmembers, said band and said hub in assembled relationship, the end wallsof said members insulating said tabs from the end surfaces of the hub.

4. In a commutator, a cylindrical metal hub, means for insulating thecylindrical and end surfaces of said hub, a plurality of commutator barscircumferentially disposed around the in sulated hub, anchor tabsextending from the ends of said bars and being bent inwardly around theend of said hub for securing the bars to the hub, and a tongue struckout from each of the tabs at one end of the commutator, the tonguesbeing secured to the tabs in the bent portions of the latter and freefrom unbent portions of the bars, whereby the tongues extend at an angleto said unbent portions.

5. In an armature, a shaft, a winding on said shaft, -a commutatormounted on said shaft comprising a cylindrical metal hub, means forinsulating the cylindrical and end surfaces of said hub, a plurality ofcommutator bars circumferentially disposed around the insulated hub,anchor tabs extending from the ends of said bars and being bent inwardlyaround the end of said hub for securing the bars to the hub and a tongueprojecting outwardly from each bar and extending at an angle away fromsaid winding, and leads from said winding looped around said tongues andclamped between the tongues and adjacent portions of said commutatorbars.

6. In a commutator, a cylindrical metal hub having an axially extendingperipheral flange at each end thereof, a pair of insulating members eachhaving a cylindrical skirt portion and an end wall conforming to theflanged end of said hub, said insulating members enclosing said hub toinsulate the cylindrical and end surfaces thereof, a plurality ofcommutator bars circumferentially disposed around the insulated hub, ananchor tab extending from each end of each bar, said tabs being bentinwardly around said flanges to secure said bars, said insulatingmembers and said hub in assembled relationship, and a tongue struck outfrom a bent portion of each of the tabs at one end of the commutator.

7. A metal commutator blank comprising a continuous center portion and aplurality of projections extending laterally from opposite side edgesthereof, each projection having a root portion with substantiallyparallel side edges and a tip portion tapering outwardly from the rootportion whereby the center portion will be firmly supported during asubsequent cutting operation.

8. A metal commutator blank comprising a continuous central portion anda plurality of projections extending laterally from opposite side edgesthereof, and a tongue struck out from each of the projections on oneside of said central portion.

9. A metal commutator blank'comprising a continuous central portion anda plurality of projections extending laterally from opposite side edgesthereof, each projection having a straight sided root portion and atapered tip portion, and a tongue struck out from each of theprojections on one side of said central por-' tion. said tongues beingjoined to the projections at a distance from said central portionsubstantially equal to the lateral extent of said root portions andextending inwardly towards said central portion.

ERIC C. WAHIBERB.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,207,359 Aunero Dec. 5, 19181,323,696 Kaisllng Dec. 2, 1919 1,550,528 Fitzgerald A118. 18, 19251,578,793 Apple Mar. 30, 1928 1,813,333 Wilson July 7, 1931 1,898,929Apple Feb. 21, 1933 2,211,979 Kuchta Aug. 20, 1940 2,451,500 Le GreidOct. 19, 1948

